1. Field of the Invention
The invention relates generally to the structure of a trailing arm suspension that is used in a vehicle. More specifically, the invention relates to the structure of a lightweight and high-performance trailing arm suspension and a lightweight and high-performance axle carrier.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-08-197926 describes the structure of a trailing arm suspension in which a curved trailing arm is directly welded to an axle carrier.
Japanese Patent Application Publication No. JP-A-2004-322913 describes the structure of a trailing arm suspension in which a longer trailing arm is provided so as to be passed through and fixed to an axle carrier.
FIG. 1 schematically illustrates the positional relationship between a trailing arm T and an axle carrier S, in the lateral direction of a vehicle, in a trailing arm suspension. FIG. 1 shows a right rear wheel viewed from the top of the vehicle.
The wheel-side end of the trailing arm T is directly welded to the axle carrier S in order to provide a lightweight trailing arm suspension having high stiffness. In such structure, the axle carrier S is a plate-like member that extends in substantially the longitudinal direction of the vehicle, as shown in FIG. 1. An axle bearing (not shown), which rotatably supports a wheel W, is fitted to the outboard side of the axle carrier S. Also, the wheel-side end of the trailing arm T is directly welded to the inboard side of the axle carrier S.
In order to function well, the trailing arm T needs to extend in substantially the longitudinal direction of the vehicle. Also, the trailing arm T needs to be fitted a vehicle body so as to be pivotable, in substantially the vertical direction of the vehicle, about an axis that extends in substantially the lateral direction of the vehicle. Consequently, an angle θ1, which the trailing arm T forms with the axle carrier S when the wheel-side end of the trailing arm T is butt-welded to the axle carrier S, is small, as shown in FIG. 1.
However, decreases in the angle, at which the trailing arm T butts against the axle carrier S, reduce ease in the welding operation. Accordingly, with the structure, in which the wheel-side end of the trailing arm T is directly welded to the axle carrier S, the butt-welding operation is difficult to perform.
FIG. 2 schematically illustrates the positional relationship between a trailing arm T and an axle carrier S, in the vertical direction of a vehicle, in a trailing arm suspension. FIG. 2 illustrates the side view of a right rear wheel viewed from a position inboard of the axle carrier S. FIG. 2 shows the structure for a four-wheel drive vehicle in which the axle carrier S has a drive shaft fitting structure D.
As shown in FIG. 2, when the structure, in which the wheel-side end of the trailing arm T is directly welded to the axle carrier S, is employed in a four-wheel drive vehicle, the trailing arm T passes through and is directly welded to the axle carrier S, at a position below a hole through which the drive shaft is fitted. Accordingly, the length of the trailing arm T needs to be longer in the backward direction of the vehicle, in comparison to when this structure is employed in a front-wheel drive vehicle. Also, in the trailing arm suspension structure used for the four-wheel drive vehicle above, the length of the axle carrier S needs to be longer in the downward direction of the vehicle. In other words, the axle carrier S for the front-wheel drive vehicle and the axle carrier S for the four-wheel drive vehicle cannot share the same design. Also, the axle carrier S for the four-wheel drive vehicle is heavier than the axle carrier S for the front-wheel drive vehicle.
Although not shown in FIG. 1, a harness of an ABS sensor, which extends from the axle bearing (not shown) fitted to the outboard side of the axle carrier S, is routed to the inside of the vehicle through through-holes formed in the axle carrier S and the trailing arm T in the trailing arm suspension. However, routing the harness in such a manner makes it difficult to attach/detach a connector.